The present invention relates to a polytetrafluoroethylene (PTFE) resin powder for molding which contains a heat resistant aromatic polyoxybenzoyl ester resin powder, undergoes less separation of the heat resistant resin powder and has a high apparent density and a high powder flowability. A molded article produced from such a resin powder has a high elongation which has not been obtained so far and is suitable for not only a sealing material such as a packing and gasket but also a sliding material such as a lubrication-free bearing, diaphragm, bellows, tube, hose, casing, lining material, back-up ring, bearing, etc.
The heat resistant aromatic polyoxybenzoyl ester resin powder is known as an organic filler for a PTFE molding powder and is excellent in that the attack by it upon an opposite material is less than that by an inorganic filler. However there is a problem that a phenomenon of separation of a filler arises, that is, the filler is separated from a granulate when the filler is granulated with the PTFE molding powder in water and thereby a final molded article is inferior in a dispersibility of the filler. As a result, an elongation of the obtained molded article is small and therefore in case of the use as an O-ring, etc., fitting work thereof becomes difficult.
An object of the present invention is to provide a resin powder for molding which undergoes less separation of the filler irrespective of the heat resistant aromatic polyoxybenzoyl ester resin powder being contained therein as the filler, has a high apparent density and a high powder flowability and gives a molded article having a high elongation, and also to provide a preparation process of the resin powder.
Namely, the present invention relates to a resin powder for molding which comprises (A) 35 to 98% by weight of a PTFE powder having an average particle size of not more than 120 xcexcm, (B) 35 to 2% by weight of a heat resistant aromatic polyoxybenzoyl ester resin powder subjected to water repelling treatment and (C) 30 to 0% by weight of an inorganic filler as an optional component, has an apparent density of not less than 0.6 g/cm3 and an average particle size of not more than 800 xcexcm, and provides a molded article having an elongation at break of not less than 20%.
When the resin powder for molding comprises two components of the PTFE powder (A) and the specific water-repelling-treated heat resistant resin powder (B), it is preferable that an amount of the PTFE powder (A) is from 65 to 98% by weight and an amount of the specific water-repelling-treated heat resistant resin powder (B) is from 35 to 2% by weight. Further when the inorganic filler (C) is added thereto, it is preferable that an amount of the powder (A) is from 35 to 97% by weight, an amount of the specific water-repelling-treated heat resistant resin powder (B) is from 35 to 2% by weight and an amount of the inorganic filler (C) is from 30 to 1% by weight.